Water Deprivation Test Wdt Procedure

Continue usual medications up to the morning of the test with the omission of desmopressin (dDAVP, Ferring) for 24 h. Fluids may be taken as normal until 07.30 h the day of testing with a light breakfast at 06.30 h. Caffeine and smoking should be discontinued from midnight.

Fluid intake and urine output from midnight should be recorded.

The WDT should be performed under direct observation. No fluid should be available in the room—taps should be removed from sinks.

The basal weight is recorded and no oral intake permitted after 07.30 h. The patient is reweighed at 4, 6, 7, and 8 h into the test. If >3% initial body weight is lost, the serum osmolality should be urgently measured.

After 8 h, the osmolalities should be reviewed and a decision made as to whether the test should continue for a further period. Once serum osmolality has reached a plateau, and/or the urine output has not decreased, dDAVP 2.0 Mg intramusculary should be administered with permission to drink free fluids. Urine samples should be collected for a further 4 h.

Sampling

All urinary voidings should be measured and recorded as detailed in the accompanying table.

Time (h)

Hr

Urine sample

Weigh

Time

Hr

Plasma sample

0l30

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